It should be fine using your other database access library. I think you'll probably want to import the libraries from each controller file. And won't need to put any of that stuff in model files.
I think reading chapters 00-07 in the Book are a good start (08 if you are using registration/login). And then just dive in and start programming. There's a lot of existing code to read and review. For example the appadmin.py controller (except that it is DAL-heavy).
